U.S. patent number 9,127,694 [Application Number 13/597,450] was granted by the patent office on 2015-09-08 for high-flow electro-hydraulic actuator.
This patent grant is currently assigned to Woodward, Inc.. The grantee listed for this patent is John J. Been, Kevin E. Greeb, Philip A. LaFleur, Jonathan P. Workman. Invention is credited to John J. Been, Kevin E. Greeb, Philip A. LaFleur, Jonathan P. Workman.
United States Patent |
9,127,694 |
Greeb , et al. |
September 8, 2015 |
High-flow electro-hydraulic actuator
Abstract
Embodiments of the invention provide a high-reliability,
cost-effective electro-hydraulic servo-valve assembly that is not
susceptible to failure caused by contaminated fluid. In particular
embodiments, the electro-hydraulic servo-valve assembly includes a
rotary valve that may be actuated by either a direct-coupled
Limited Angle Torque (LAT) motor, a geared, brushless DC motor, or
some other rotary electric actuating element with an integrated
driver circuit. In particular embodiments, the rotary valve element
made up of an outer sleeve element and an inner spool element, with
matching ports and slots, respectively.
Inventors: |
Greeb; Kevin E. (Fort Collins,
CO), LaFleur; Philip A. (Loveland, CO), Workman; Jonathan
P. (Loveland, CO), Been; John J. (Fort Collins, CO) |
Applicant: |
Name |
City |
State |
Country |
Type |
Greeb; Kevin E.
LaFleur; Philip A.
Workman; Jonathan P.
Been; John J. |
Fort Collins
Loveland
Loveland
Fort Collins |
CO
CO
CO
CO |
US
US
US
US |
|
|
Assignee: |
Woodward, Inc. (Fort Collins,
CO)
|
Family
ID: |
47828984 |
Appl.
No.: |
13/597,450 |
Filed: |
August 29, 2012 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20130062542 A1 |
Mar 14, 2013 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61532922 |
Sep 9, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F15B
13/0406 (20130101); F16K 27/048 (20130101); F15B
13/0444 (20130101); F16K 31/041 (20130101); F16K
11/076 (20130101); F16K 27/041 (20130101); Y10T
137/86863 (20150401) |
Current International
Class: |
F16K
31/02 (20060101); F15B 13/044 (20060101); F15B
13/04 (20060101); F16K 11/076 (20060101); F16K
31/04 (20060101); F16K 27/04 (20060101) |
Field of
Search: |
;251/129.11,129.12,129.13,384 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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19836042 |
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Feb 2000 |
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DE |
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10240852 |
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Mar 2004 |
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DE |
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962794 |
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Jul 1964 |
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GB |
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1244976 |
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Sep 1971 |
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GB |
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Other References
Parker Servovalves; date last visited Oct. 11, 2012; 2 pages
printed from internet;
http://www.parker.com/portal/site/PARKER/menuitem.7100150cebe5b-
bc2d6806710237ad1ca/?vgnextoid=f5c9b5bbec622110VgnVCM10000032a71dacRCRD&vg-
nextfmt=DE&vgnextdiv=&vgnextcatid=1537927&vgnextcat=SERVOVALES.
cited by applicant .
Bosch Rexroth Hydraulic Servos; date last visited Oct. 11, 2012; 1
page printed from internet;
http://www.boschrexroth.com/country.sub.--units/america/united.sub.--stat-
es/sub.sub.--websites/brus.sub.--brh.sub.--i/en/products.sub.--ss/08.sub.--
-proportional.sub.--servo.sub.--valves/06.sub.--servo.sub.--valves/index.j-
sp. cited by applicant .
Woodward Direct Drive Servovalves; date last visited Oct. 9, 2012;
1 page printed from internet;
http://www.woodward.com/DirectDrive.sub.--Servovalves.aspx. cited
by applicant .
Woodward Electro-Hydraulic Servovalves; dated last visited Oct. 9,
2012; 1 page printed from internet;
http://www.woodward.com/servovalves.aspx. cited by applicant .
MOOG Electrohydraulic Valves . . . A Technical Look; date last
visited Oct. 9, 2012; 24 pages printed from internet;
http://www.moog.com/literature/ICD/Valves-Introduction.pdf. cited
by applicant.
|
Primary Examiner: Schneider; Craig
Assistant Examiner: Barss; Kevin
Attorney, Agent or Firm: Reinhart Boerner Van Deuren
P.C.
Parent Case Text
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
This patent application claims the benefit of U.S. Provisional
Patent Application No. 61/532,922, filed Sep. 9, 2011, the entire
teachings and disclosure of which are incorporated herein by
reference thereto.
Claims
What is claimed is:
1. A valve assembly comprising: a housing including at least one
port; and a rotary valve disposed within the housing, the rotary
valve comprising: an outer sleeve with at least one port aligned
with the at least one port of the housing; a spool rotationally
disposed within the sleeve, the spool including a shaft and at
least one valve element disposed along the shaft, the at least one
valve element including at least one port formed thereon; a first
and a second anti-friction element supporting opposing ends of the
shaft of the spool; a rotary electric actuating device coupled to
an end of the shaft, the rotary electric actuating device operable
to rotate the spool to selectively align the at least one port of
the spool with the at least one port of the sleeve; and wherein the
at least one port of the spool includes a bottom edge and a pair of
opposed side edges depending away from the bottom edge such that
the at least one port has a generally U-shaped opening with an open
end, with one of the pair of opposed side edges forming a control
edge having a first wall thickness, and wherein the other one of
the pair of side edges has a second wall thickness, the first wall
thickness less than the second wall thickness.
2. The valve assembly of claim 1, wherein the first wall thickness
of the control is about 0.015 inches to about 0.060 inches.
3. The valve assembly of claim 2, wherein the thickness of the
control edge is about 0.030 inches.
4. A valve assembly comprising: a housing; and a rotary valve
disposed within the housing, the rotary valve comprising: an outer
sleeve having a plurality of ports and defining a center line of
the rotary valve; a spool concentrically and rotationally disposed
within the sleeve along the center line thereof, the spool
including a shaft and a plurality of ports, wherein the plurality
of ports of the sleeve and the plurality of ports of the spool are
radially equally spaced such that pressure loading on the spool is
balanced; a first and a second anti-friction element, the first and
second anti-friction elements supporting opposing ends of the
shaft; a rotary electric actuating device coupled to an end of the
shaft adjacent one of the first and second anti-friction elements,
the rotary electric actuation device operable to selectively rotate
the spool; and first and second isolation seals, the first
isolation seal adjacent to the first anti-friction element and
sealingly engaging the shaft, the second isolation seal adjacent to
the second anti-friction element and sealingly engaging the shaft,
the first and second isolation seals axially interposed between the
first and second anti-friction elements.
5. The valve assembly of claim 4, wherein the first and second
anti-friction elements are deep groove ball bearings.
6. The valve assembly of claim 4, wherein the rotary electric
actuating device is one of a limited angle torque motor, a geared
brushless DC motor, or a solenoid.
7. The valve assembly of claim 4, wherein the spool is a one-piece
construction machined from a single blank.
8. The valve assembly of claim 4, wherein the spool is a
multi-piece construction, with the at least one valve element
mechanically attached to the shaft.
9. The valve assembly of claim 4, wherein the rotary electric
actuating device is isolated from all hydraulic fluid cavities of
the valve assembly by one or more sealing elements.
Description
FIELD OF THE INVENTION
This invention generally relates to electro-hydraulic actuators or
servo-valves.
BACKGROUND OF THE INVENTION
Electro-hydraulic servo-valves are widely used to control the flow
of hydraulic fluid into and out of power cylinders that are used to
control, for example, the flow or pressure of fuel, air, or steam.
However, some conventional servo-valves do not operate very
efficiently or can fail when regulating the flow of contaminated
fluids. Further, traditional servo-valves can be adversely affected
by vibration. Vibration in the axial direction of the spool can
move it from the desired position causing a position error of the
actuator. Additionally, conventional servo-valves are typically
non-compliant with Div. 1/Zone 1 hazardous location
(explosion-proof) requirements. Typically, explosion-proof
servo-valves are considered "specials" and are usually expensive
devices requiring long lead times.
Further, many conventional servo-valves are two stage using a
linear spool type flow control valve as the main fluid flow control
element. Generally, tight radial clearances are used to help keep
the sliding spool centered within the outer element and reduce
fluid leakage. It is possible that these tight clearances can
become further constricted if there is contamination in the fluid
flow causing the spool to stick, for if the fluid is not filtered
to extreme cleanliness levels. The need to maintain tight
tolerances leads to time-consuming manufacturing processes and
testing of the device, and drives up the cost of traditional
servo-valves.
Also, in some cases, contamination in the fluid flow may restrict
flow through nozzles in the first stage of the servo-valve. In
other cases, small diameter wire used for the torque motor winding
is subject to strain failure and is another source of poor
reliability. Some conventional servo-valves require hydraulic
pressure to move the spool valve to its failsafe position. If the
filter supplying the first stage element plugs, or pressure is lost
for some other reason, there is a risk that the servo-valve will
not easily move to the failsafe position.
In some cases, conventional direct drive or proportional valves
(rotary or linear) often have a "wet" drive motor that can collect
iron particles from the oil, which can eventually decrease the
performance of the valve. Further, conventional direct drive or
proportional valves (rotary or linear) that have high flow capacity
have high flow forces acting on the moving element. This requires a
high-force electrically powered first stage that can have high
power requirements and/or be too slow for good dynamic control.
Also, conventional direct drive or proportional valves often only
have a single control signal input and a single power input.
Failure of either input causes the servo-valve to no longer
function.
Embodiments of the invention provide an improvement over the state
of the art in electro-hydraulic actuators. These and other
advantages of the invention, as well as additional inventive
features, will be apparent from the description of the invention
provided herein.
BRIEF SUMMARY OF THE INVENTION
In one aspect, embodiments of the invention provide a
high-reliability, cost-effective servo-valve assembly that is not
susceptible to failure caused by contaminated fluid. In particular
embodiments, the rotary control valve may be actuated by a
direct-coupled Limited Angle Torque (LAT) motor, a geared,
brushless DC motor, or some other rotary electric actuating element
with an integrated driver circuit.
Embodiments of the invention include a rotary control valve element
made up of an outer sleeve element and an inner spool element, with
matching ports and/or slots, respectively. An inner spool element
is mated essentially concentrically to the outer sleeve element by
anti-friction elements. In an embodiment of the invention, the
anti-friction elements are deep-groove ball bearings. In particular
embodiments, the valve flow control ports are arranged essentially
radially and equally-spaced such that pressure loading on the spool
is balanced so as to not side-load the spool one way or the
other.
For example, if the rotary control valve had two control ports,
they would be arranged 180 degrees apart, if the valve had three
control ports, they would be arranged 120 degrees apart, and so on.
The valve could be configured in a two way, three-way, four-way, or
other multi-functional valve configuration. In a particular
embodiment, four-way valve embodiment includes first and second
control flow ports connected to the controlled element, which may
be a hydraulic power cylinder. In either configuration, rotation in
either direction from the null position (i.e., no flow out of any
ports) will direct flow from the supply to the first control flow
port and from the second control flow port to the drain, or from
the supply to the second control flow port and from the first
control flow port to the drain.
The position of the rotary control valve is controlled by the
rotary electric actuating element, which is a LAT in certain
embodiments of the invention. In certain embodiments, the rotary
actuating element is controlled by the integrated driver circuit
board, using an electronic rotary position sensor to monitor valve
position. In particular embodiments, a return spring is attached to
the inner valve element to provide a fail-safe rotation of the
spool in the event of loss of signal to the rotary electric
actuating element.
In another aspect, embodiments of the invention provide an
electro-hydraulic actuator assembly that includes a housing, and a
rotary control valve disposed within the housing, the rotary
control valve having one or more control flow ports. In particular
embodiments, the rotary control valve is actuated by one of a
limited angle torque motor and a geared, brushless DC motor. In a
further embodiment, the housing is compliant with Div. 1/Zone 1
hazardous location requirements.
In one embodiment, the invention provides an electro-hydraulic
actuator assembly. The electro-hydraulic actuator assembly includes
a housing with at least one port. A rotary control valve is
disposed within the housing. The rotary control valve includes an
outer sleeve with at least one port aligned with the at least one
port of the housing. A spool is rotationally disposed within the
sleeve. The spool includes a shaft and at least one valve element
disposed along the shaft. The at least one valve element includes
at least one port formed thereon. A first and a second
anti-friction element support opposing ends of the shaft of the
spool. A rotary electric actuating device is coupled to an end of
the shaft. The rotary electric actuating device is operable to
rotate the spool to selectively align the at least one port of the
spool with the at least one port of the sleeve.
In certain other subsidiary embodiments, the sleeve incorporates a
radially outwardly directed spot face lead-in area adjacent to at
least one port of the sleeve. At least one valve element includes a
radially inwardly directed contoured spot face lead-in area
adjacent to at least one port of at least one valve element.
In certain embodiments, the spool is a one piece construction
machined from a single blank. In certain other embodiments, the
spool is a multi-piece construction, with at least one valve
element mechanically attached to the shaft of the spool. As a
subsidiary feature of this embodiment, the shaft of the spool can
include at least one pilot diameter on the shaft for receipt of a
hub of at least one valve element. In certain embodiments, the
rotary electric actuating device is one of a limited angle torque
motor, a geared brushless DC motor, or a solenoid.
In certain embodiments, the actuator assembly additionally includes
a return spring for biasing the spool to a failsafe position in the
event of a failure in the rotary electric actuating device. The
return spring can be coupled to an end of the shaft of the spool
opposite the end of the shaft that is coupled to the rotary
electric actuating device.
In a subsidiary embodiment, the first and second anti-friction
elements are first and second bearings. The first bearing is
axially disposed along the shaft of the spool interior of the
return spring. The second bearing is axially disposed along the
shaft of the spool interior of the rotary electric actuating
device.
In another embodiment according to the invention, an
electro-hydraulic actuator assembly is provided. The
electro-hydraulic actuator assembly includes a housing. A rotary
control valve is disposed within the housing. The rotary control
valve includes an outer generally cylindrical sleeve having a bore
therethrough. A spool is concentrically and rotationally disposed
within the bore. The spool includes a shaft and at least one valve
element disposed along the shaft. A first and a second
anti-friction element are also provided wherein the first
anti-friction element supports one end of the shaft while the
second anti-friction element supports the other end of the shaft.
The at least one valve element is interposed between the first and
second anti-friction elements. The spool is held in a concentric
clearance fit relationship relative to the sleeve by the first and
second anti-friction elements. A rotary electric actuating device
is coupled to an end of the shaft adjacent one of the first and
second anti-friction elements. The rotary electric actuation device
is operable to selectively rotate the spool. In a subsidiary
embodiment, the valve/actuator housing is compliant with flameproof
methods of protection suitable for Div. 1/Zone 1 hazardous
locations.
In a subsidiary embodiment, the first and second anti-friction
elements are deep-groove ball bearings. In another subsidiary
embodiment, the housing is compliant with Div. 1/Zone 1 hazardous
location requirements. In certain other subsidiary embodiments, the
rotary electric actuating device is one of a limited angle torque
motor, a geared brushless DC motor, or a solenoid.
In certain embodiments, the spool is a one-piece construction
machined from a single blank. In certain other embodiments, the
spool is a multi-piece construction, with the at least one valve
element mechanically attached to the shaft.
In yet another embodiment according to the invention, an
electro-hydraulic actuator assembly is provided. An
electro-hydraulic actuator assembly according to this embodiment
includes a housing. A rotary control valve is disposed within the
housing. The rotary control valve includes an outer sleeve having a
plurality of ports and defining a center line of the rotary control
valve. A spool is concentrically and rotationally disposed within
the sleeve along the center line thereof. The spool includes a
plurality of ports. The plurality of ports of the sleeve and the
plurality of ports of the spool are radially equally spaced such
that pressure loading on the spool is balanced. A first and a
second anti-friction element are also provided. The first and
second anti-friction elements support opposing ends of the shaft. A
rotary electric actuating device is also provided that is coupled
to an end of the shaft adjacent one of the first and second
anti-friction elements. The rotary electric actuation device is
operable to selectively rotate the spool.
In a subsidiary embodiment, the valve/actuator housing is compliant
with flameproof methods of protection suitable for Div. 1/Zone 1
hazardous locations. In a subsidiary embodiment, the first and
second anti-friction elements are deep groove ball bearings. In yet
another subsidiary embodiment, the rotary electric actuating device
is one of a limited angle torque motor, a geared brushless DC
motor, or a solenoid.
In certain embodiments, the spool is a one-piece construction
machined from a single blank. In certain other embodiments, the
spool is a multi-piece construction with the at least one valve
element mechanically attached to the shaft.
Other aspects, objectives and advantages of the invention will
become more apparent from the following detailed description when
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings incorporated in and forming a part of the
specification illustrate several aspects of the present invention
and, together with the description, serve to explain the principles
of the invention. In the drawings:
FIG. 1 is a perspective view of an electro-hydraulic actuator
assembly, constructed in accordance with an embodiment of the
invention;
FIG. 2 is a cross-sectional view of the electro-hydraulic actuator
assembly of FIG. 1; and
FIG. 3 is a perspective view of a portion of a rotary control
valve, constructed in accordance with an embodiment of the
invention.
FIG. 4 is a cross-sectional view of another embodiment of an
electro-hydraulic actuator assembly, constructed in accordance with
teachings of the invention;
FIG. 5 is a perspective exploded view of a spool of the rotary
control valve of the embodiment of FIG. 4;
FIG. 6 is a partial perspective cross-sectional view of the spool
of FIG. 5;
FIG. 7 is a partial perspective view of a sleeve of the rotary
control valve of the embodiment of FIG. 4; and
FIG. 8 is a perspective view of another embodiment of a spool
constructed in accordance with the teachings of the present
invention.
While the invention will be described in connection with certain
preferred embodiments, there is no intent to limit it to those
embodiments. On the contrary, the intent is to cover all
alternatives, modifications and equivalents as included within the
spirit and scope of the invention as defined by the appended
claims.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a perspective view of a servo-valve assembly with
integrated electrical actuator 18, constructed in accordance with
an embodiment of the invention. The assembly includes a housing 20
with a rotary control valve 22 (See FIG. 2) positioned therein and
operable to selectively direct fluid flow into and out of various
ports of the assembly. The housing 18 (as well as various internal
components thereof) is a Div. 1/Zone 1 rated, IP 56 enclosure. As
will be explained in greater detail below, the assembly overcomes
existing problems in the art by providing a highly reliable, high
flow, low actuation force flow control device that is pressure
insensitive and vibration and contaminant resistant. The actuator
18 dislcosed herein may be employed in the context of trip valves,
relief valves, reducing valves, as well as in the context of the
control of hydraulic fluid, e.g. on/off control, flow modulation,
directional control, pressure control, etc.
Turning now to FIG. 2, embodiments of the invention include a
rotary control valve 22 made up of an outer sleeve element 24 and
an inner spool element 26, with matching ports 28 and slots 30,
respectively. Note that slots 30 function as flow ports, and are
thus referred to herein as ports 30. The ports 28, 30 are arranged
essentially radially and equally-spaced, such that pressure loading
on the spool 26 is balanced so as to not side-load the spool 26 one
way or the other. The rotary control valve 22 may be actuated by
rotary electric actuating element 32, which in the embodiment of
FIG. 2 is a direct coupled Limited Angle Torque (LAT) motor coupled
to spool 26. Each slot shaped port 30 of spool 26 is formed on a
valve member thereof and includes a bottom edge and opposed side
edges depending from the bottom edge.
The rotary electric actuating element 32 has a high reliability as
it is separated from the fluid and kept dry through the use of
isolation seals 36, 38. This keeps the rotary electric actuating
element 32 free of contamination that can build up and inhibit
motion. Also, in particular embodiments, the rotary electric
actuating element 32 uses large-diameter wire for the coil
windings. This large-diameter wire is resistant to the strain and
small movements that can cause failure in small torque motor
windings. In alternate embodiments, the rotary control valve may be
actuated by a geared brushless DC motor, a solenoid, or other
rotary electric actuating element with an integrated driver
circuit. In a particular embodiment, the inner spool element 26 is
mated essentially concentrically to the outer sleeve element 24 by
anti-friction elements 34. In a more particular embodiment, the
anti-friction elements 34 are deep groove ball bearings.
FIG. 3 is a perspective view of a portion of the rotary control
valve 22 shown in FIG. 2. In embodiments of the rotary control
valve 22 having two control ports, they would be arranged 180
degrees apart, in embodiments of the rotary control valve 22 having
three control ports, they would be arranged 120 degrees apart, and
so on. The rotary control valve could be configured in a three-way
or four-way control valve configuration. A four-way valve
embodiment is shown in FIG. 3, with a first control flow port ("C1"
in FIG. 3), and a second control flow port ("C2" in FIG. 3) both
connected to the controlled element, which may be a hydraulic power
cylinder.
In either configuration, rotation in either direction from the null
position (no flow out of any ports), will direct flow from the
supply ("S" in FIG. 3) to C1, and from C2 to the drain ("D" in FIG.
3), or from the supply to C2 and from C1 to the drain. Note that
each of ports labeled D, C1, C2, S are isolated from one another
through the use of seals 58 arranged on sleeve 24.
Returning now to FIG. 2, the position of the rotary control valve
22 is controlled by the rotary electric actuating element 32, an
LAT in the embodiment shown in FIG. 2. The rotary actuating element
32 is controlled by the integrated driver circuit board 42, using
an electronic rotary position sensor 44 to monitor valve position.
In certain embodiments, a return spring 46 is attached to the inner
spool element 26 to provide a fail-safe rotation of the spool 26 in
the event of loss of signal to the rotary electric actuating
element 32. The return spring 46 will close or move the valve,
particularly the spool 26, to the failsafe position upon loss of
power and does not depend on hydraulic pressure to ensure that the
valve goes to the failsafe position.
The servo-valve in the device described herein is designed to
operate with fluid having a cleanliness of ISO 4406 20/18 or
cleaner. It has a unique rotating valve, as opposed to linear,
which is supported by rotary anti-friction bearings 34 concentric
with the outer stationary sleeve element 24 resulting in low
actuation forces. Clearances between the moving and stationary
valve elements 24, 26 are larger than the contamination particles,
preventing contamination from jamming the valve. In an exemplary
embodiment, the radial clearance gap, i.e. the difference between
the radius of the outer periphery of the spool and the radius of
the bore extending through sleeve 24, is between about 0.0005'' and
about 0.005''. However, those skilled in the art will recognize
that the other radial clearances are conceivable depending upon
application, particularly expected contaminant particle size.
Pressure loading on the rotary control valve 22 is radially
balanced, eliminating radial deflections that could cause drag from
contact with portions of the outer non-rotating sleeve element 24.
Also, pressure loading on the rotary control valve 22 is axially
balanced, eliminating friction or drag from bearings 34.
Additionally, in particular embodiments, flow force reduction
techniques are employed to ensure that flow forces are low,
ensuring that high actuator force margins are maintained regardless
of system pressure. Because the forces on the rotary control valve
22 are low, a servo-valve capable of high flow rates without
multiple amplification stages is achievable using a low-power
rotary electric actuation element 32.
In a particular embodiment of the invention, the electrical
actuator assembly has integrated electronics for servo-valve and
final output actuator position control in the form of a driver
circuit 42. Further, the electrical actuator assembly 18 supports
dual control setpoint inputs and dual power inputs which allow the
unit to be powered from independent supplies and from independent
controllers, increasing overall reliability. The electrical
actuator assembly 18 has provisions for high speed unit/unit
redundant health monitoring links. This allows for the use of
redundant servo-valves for very critical applications, wherein the
second servo-valve maintains operation if the first servo valve or
electronics were to fail. Dual final actuator position feedback
loops are utilized to maintain operation even in the event of a
feedback sensor fault. In an embodiment of the invention, the
electronics in the electro-hydraulic actuator assembly are capable
of sustained operation at 85.degree. C., which is higher than that
for electronics in conventional proportional valves.
Turning now to FIG. 4, another embodiment of a servo-valve assembly
with integrated electrical actuator 118 is illustrated. This
embodiment is the same as the embodiment described at FIGS. 1-3,
with several exceptions as described below. Indeed, the assembly
118 includes a housing 120 which carries a rotary control valve 122
therein. As was the case with the embodiment of FIGS. 1-3, housing
120 may be a Div. 1/Zone 1 IP 56 rated enclosure.
The rotary control valve 122 includes a stationary sleeve 124, with
a plurality of ports 128, which surrounds a rotatable valve spool
126, also with a plurality of ports 130. Ports 128, 130 are equally
radially spaced so that control valve 122 is balanced. Further, as
was the case with the embodiment of FIGS. 1-3, a plurality of seals
158 are arranged along the sleeve 124 to isolate the various ports
128, 130 from one another. The valve spool 126 is held accurately
and concentrically within the sleeve 124 through the use of
anti-friction elements 134. The spool 126 is coupled to a rotary
electric actuating device 132 which is maintained in a dry state
through the use of isolation seals 136, 138.
The rotary electric actuating device 132 is a rotary solenoid in
this design. Such a device is highly reliable, and provides
significant power cost savings given its lower power of actuation.
This particular rotary electric actuating device 132 may be a
normally closed type rotary solenoid wherein with power applied to
the device 132, the rotary control valve 120 is held in a normally
closed position. Upon interruption of power, the rotary electric
actuating device 132 will rotate valve spool 126 to the desired
position. Those skilled in the art will recognize that the solenoid
used for electric actuating device 132 could equally be a normally
open configuration as well. Additionally, a return spring 146 may
also be provided to return valve spool 126 to a failsafe position
upon a loss of power.
With reference now to FIG. 5, the spool 126 in this design, unlike
the one-piece construction of FIGS. 1-3, is a multi-piece
construction. Spool 126 includes multiple cup shaped valve elements
150 which are attached to a spool shaft 152 through welding, or any
other mechanical connection means sufficient to ensure the
functionality of spool 126. Spool shaft 152 can include pilot
diameters 154 for receiving a connecting hub 156 of each cup shaped
valve element 150 at its point of connection to spool shaft 152. It
will be recognized that this multi-piece assembly for spool 126 is
easier and less costly to produce than the one piece structure of
FIGS. 1-3 from a machining stand point.
With reference now to FIG. 6, each cup shaped valve element 150
includes smooth interior surface contours 160 which permit a
reduction in flow forces as fluid is directed through each valve
element 150. Further, each port 130 of spool 126 is provided with a
radially inwardly directed contoured spot face representing lead in
area 162 which also provides for a reduction in flow forces. Each
contoured spot face is a generally smooth, curved transition, as
opposed to a sharp edge that would otherwise define the periphery
of the port. Each lead in area 162 terminates at a thin control
edge 190 that has a reduced thickness to reduce flow forces. In
certain embodiments, the control edge 190 has a thickness of about
0.015 inches to about 0.060 inches, and preferably about 0.030
inches. It has been found that a control edge thickness of below
about 0.015 inches can lead to deflection and erosion, while a
control edge thickness of above about 0.060 inches can lead to
undesirably large flow forces.
Similarly, and with reference now to FIG. 7, each port 130 of
sleeve 124 includes a radially outwardly directed spot face, lead
in area 164, which also provides for a reduction in flow forces. As
was the case with the embodiment of FIGS. 1-3, the rotary control
valve 122 may be configured having two control ports wherein they
would be arranged 180 degrees apart. In embodiments of the rotary
control valve 122 having three control ports, they would be
arranged 120 degrees apart, and so on. The rotary control valve 122
could be configured in a three-way or four-way control valve
configuration. A four-way valve embodiment is shown in FIGS.
4-7.
Turning now to FIG. 8, another embodiment of a spool 226 is
illustrated. This embodiment of spool 226 is also machined as a
one-piece construction from a single blank, similar to spool 26.
This embodiment of spool 226 also includes reduced thickness
control edges 290 similar to spool 126, as will be described in
greater detail below.
Spool 226 includes a plurality of valve members 250 formed on a
shaft 252. The outer most valve members 250 include generally slot
shaped ports 230a, while the interior central valve member 250
includes generally slot shaped ports 230b. From inspection of FIG.
8, it can be seen that ports 230a and 230b each have an irregular
shape, which will be discussed in turn.
Slots 230a include a bottom edge 270, and side edges 272, 274
depending away from bottom edge 270. The side edges 272, 274 are in
an opposed spaced relationship, with one side edge 274 including a
small indentation 276 formed along its length. As can be seen at
the right-most valve member 250 in FIG. 8, each slot 230a, and more
particularly side edge 274, is a control edge 290 having a reduced
thickness of about 0.015 inches to about 0.060 inches, and
preferably about 0.030 inches.
Slots 230b also include a bottom edge 280, and opposed side edges
282, 284 depending away from bottom edge 280. One side edge 284
includes a small indentation 286 formed along its length.
Furthermore, side edge 284 represents a control edge 290 having a
reduced thickness of about 0.015 inches to about 0.060 inches, and
preferably about 0.030 inches. Additionally, side edge 282 is
non-parallel with side edge 284, and terminates in a rounded corner
288.
Those skilled in the art will recognize that the rotary electric
actuating device 32 of FIGS. 1-3 could equally be employed with the
multi-piece spool 126 of FIGS. 4-7, or the spool 226 of FIG. 8.
Further, the rotary solenoid embodying rotary electric actuating
device 132 of FIGS. 4-7 could equally be employed with the single
piece spool 26 construction of FIGS. 1-3, or spool 226 of FIG.
8.
As described herein, the design of the electric actuator lends
itself to lower-cost manufacturing due to the fact that the design
requires less precision and shorter assembly/test times than
conventional servo-valves. The rotary control valve is (mass)
rotationally balanced and its position is not adversely affected by
vibration. A bi-directional, high-torque rotary electric actuating
element can be used to rotate the rotary control valve. High torque
combined with the low valve actuation force provides high force
margin in both directions for shearing dirt particles
(contamination) in the oil. It does not require a return spring for
torque (or force when compared linear electric actuators) in the
reverse direction.
All references, including publications, patent applications, and
patents cited herein are hereby incorporated by reference to the
same extent as if each reference were individually and specifically
indicated to be incorporated by reference and were set forth in its
entirety herein.
The use of the terms "a" and "an" and "the" and similar referents
in the context of describing the invention (especially in the
context of the following claims) is to be construed to cover both
the singular and the plural, unless otherwise indicated herein or
clearly contradicted by context. The terms "comprising," "having,"
"including," and "containing" are to be construed as open-ended
terms (i.e., meaning "including, but not limited to,") unless
otherwise noted. Recitation of ranges of values herein are merely
intended to serve as a shorthand method of referring individually
to each separate value falling within the range, unless otherwise
indicated herein, and each separate value is incorporated into the
specification as if it were individually recited herein. All
methods described herein can be performed in any suitable order
unless otherwise indicated herein or otherwise clearly contradicted
by context. The use of any and all examples, or exemplary language
(e.g., "such as") provided herein, is intended merely to better
illuminate the invention and does not pose a limitation on the
scope of the invention unless otherwise claimed. No language in the
specification should be construed as indicating any non-claimed
element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein,
including the best mode known to the inventors for carrying out the
invention. Variations of those preferred embodiments may become
apparent to those of ordinary skill in the art upon reading the
foregoing description. The inventors expect skilled artisans to
employ such variations as appropriate, and the inventors intend for
the invention to be practiced otherwise than as specifically
described herein. Accordingly, this invention includes all
modifications and equivalents of the subject matter recited in the
claims appended hereto as permitted by applicable law. Moreover,
any combination of the above-described elements in all possible
variations thereof is encompassed by the invention unless otherwise
indicated herein or otherwise clearly contradicted by context.
* * * * *
References